Energy Expenditure Determined by Self-Reported Physical Activity Is Related to Body Fatness

BUCHOWSKI, MACIEJ S., KAREN M. TOWNSEND, KONG Y. CHEN, SARI A. ACRA, AND MING SUN. Energy expenditure determined by self-reported physical activity is related to body fatness. Obes. Res. 1999;7:23–33. Objective : Activity self-reports are a commonly used tool in assessing daily physical activity (PA) and associated energy expenditure (EE). This study examined the effect of relative body fatness (%BF) on differences between self-reported and measured duration and associated EE in healthy adults. Research Methods and Procedures: Men and women (n= 115, age 38±9 years), ranging in %BF from 7.9% to 58.9%, spent two separate days (normal and exercise) in a whole-room indirect calorimeter where EE was measured. While in the room calorimeter, subjects reported the type, intensity, and duration of each performed PA. The Compendium of Physical Activity was used to calculate the energy cost of each reported activity. The EE of all self-reported activities (EE_r) was categorized into four intensity levels, synchronized, and compared with EE from the room calorimeter (EE_m). Results : With increasing %BF, subjects significantly overestimated duration of more strenuous activities (≥4.5), while underestimating moderate activities (2.5 to 4.4 metabolic equivalents (METs)). Misreporting of duration and/or intensity caused an overestimation or underestimation of PA-associated EE at these levels. Reported EE sleep was lower than measured EE sleep, although both had similar durations. As a result, total EE_r was similar to EE_m. Discussion : Individual variability of daily total PA and associated EE generated from self-reports in adults is high. Persons with a higher %BF report duration and/or intensity of moderate to high levels of PA with lower accuracy than leaner individuals. We conclude using the Compendium of Physical Activity is not suitable for the accurate estimation of self-reported EE of AA in adults with a higher %BF.     

Ability of the Actiwatch Accelerometer to Predict Free‐Living Energy Expenditure in Young Children

Objective: To determine whether activity counts obtained with the Actiwatch monitor are associated with total expenditure and body composition in young children. Research Methods and Procedures: Actiwatch activity monitors were tested in 29 children 4 to 6 years old under field conditions over eight days. Total energy expenditure (TEE) was assessed with the doubly labeled water (DLW) technique. Correlation analyses were used to identify variables related to energy expenditure and percentage body fat. Multiple linear regression analyses were used to examine the variance in TEE and percentage body fat explained by activity counts after adjusting for relevant covariates. Results: Both average total daily activity counts (658, 816 ± 201, 657) and the pattern of activity were highly variable among subjects. TEE was significantly related to lean body mass (r = 0.45) and age (r = 0.48; p < 0.05 for both). Activity counts alone were not associated with TEE. In multiple linear regression analyses, TEE was independently associated with only lean body mass. Percentage fat mass was independently associated with body weight, being a girl, and being white, but not with average total activity counts. Discussion: Activity counts obtained with the Actiwatch under free‐living conditions do not reflect TEE in 4‐ to 6‐year‐old children and are not correlated with percentage fat mass. Therefore, average total activity counts obtained with the Actiwatch may be of limited value in identifying children at risk for becoming obese.     

Plasma Adiponectin Levels Are Not Associated with Fat Oxidation in Humans

Objective: To test the hypothesis that low adiponectin is associated with low fat oxidation in humans. Research Methods and Procedures: We measured plasma adiponectin concentrations in 75 healthy, nondiabetic Pima Indians (age, 28 ± 7 years; 55 men and 20 women; body fat, 29.7 ± 7.5%) and 18 whites [(age, 33 ± 8 years; 14 men and 4 women; body fat, 28.2 ± 10.8% (means ± SD)] whose body composition was measured by DXA and 24-hour energy expenditure (24-hour EE) by a respiratory chamber. Respiratory quotient (an estimate of whole-body carbohydrate/lipid oxidation rate) was calculated over 24 hours (24-hour RQ). Results: Before correlational analyses, waist-to-thigh ratio (WTR) and percentage of body fat (PFAT) were adjusted for age, sex, and race; 24-hour EE was adjusted for fat mass and fat-free mass, and 24-hour RQ were adjusted for energy balance. Plasma adiponectin concentrations were negatively correlated with WTR (r = −0.42, p < 0.0001) and PFAT (r = −0.46, p < 0.0001). There was no correlation between plasma adiponectin concentrations and 24-hour RQ, (r = 0.09, p = 0.36) before or after adjustment for PFAT (r = 0.001, p = 0.99, respectively, partial correlation), and no correlation was found between plasma adiponectin concentrations and 24-hour EE (r = −0.12, p = 0.27). Discussion: Our cross-sectional data do not suggest physiological concentrations of fasting plasma adiponectin play a role in the regulation of whole-body fat oxidation or energy expenditure in resting conditions. Whether administration of adiponectin to individuals with low levels of this hormone will increase their fat oxidation rates/energy expenditure remains to be established.     

Relationship of Body Composition to Body‐Fatness Estimation in Japanese University Students

Objective: To examine the relationship between self‐estimated whole body size and fatness and whole body and regional composition, and the relationship between self‐estimated whole body fatness and self‐estimated regional fatness in Japanese university students. Research Methods and Procedures: This was a cross‐sectional study using Japanese university students (110 men and 79 women). The percentage of body fat, fat mass (FM), and fat‐free mass (FFM) were measured by underwater weighing and used as body composition variables. Subcutaneous fat thicknesses were determined at seven sites by ultrasonography to estimate regional body composition, and six circumferences and four breadths to estimate regional size. Relative body size and fatness were self‐estimated using a questionnaire. Results: Only women tended to estimate themselves as being fatter than they actually were. Self‐estimated body fatness moderately correlated with the percentage of body fat (men, r = 0.41; women, r = 0.40) FM (men, r = 0.50; women, r = 0.51), and body mass index (r = 0.56 for men and 0.56 for women). After adjusting for the percentages of body fat and FM, self‐estimated fatness correlated with body mass index (r = 0.31 for men and r = 0.37 for women). Among self‐estimated regional fatness, self‐estimated abdominal fatness had the strongest correlation with self‐estimated whole body fatness in both genders. Discussion: The low correlation between estimated and actual body fatness in both genders indicates that Japanese university students, especially women, inaccurately estimate their percentage of body fat. In fact, both men and women primarily estimate their whole body fatness by body weight relative to height.     

Effect of Scalp and Facial Hair on Air Displacement Plethysmography Estimates of Percentage of Body Fat

Objective: The objective of this study was to determine the effect of body hair (scalp and facial) on air displacement plethysmography (BOD POD) estimates of percentage of body fat. Research Methods and Procedures: A total of 25 men (31.4 ± 8.0 years, 83.4 ± 12.2 kg, 181.8 ± 6.9 cm) agreed to grow a beard for 3 weeks to participate in the study. Total body density (g/cm³) and percentage of body fat were evaluated by BOD POD. To observe the effect of trapped isothermal air in body hair, BOD POD measures were performed in four conditions: criterion method (the beard was shaven and a swimcap was worn), facial hair and swimcap, facial hair and no swimcap, and no facial hair and no swimcap_. Results: The presence of only a beard (facial hair and swimcap) resulted in a significant underestimation of percentage of body fat (16.2%, 1.0618 g/cm³) vs. the criterion method (17.1%, 1.0597 g/cm³, p < 0.001). The effect of scalp hair (no swim cap worn) resulted in a significant underestimation in percentage of body fat relative to the criterion method, either with facial hair (facial hair and no swimcap; 14.8%, 1.0649 g/cm³) or without facial hair (no facial hair and no swimcap; 14.8%, 1.0650 g/cm³, p < 0.001 for both). Discussion: A significant underestimation of percentage of body fat was observed with the presence of facial hair (～1%) and scalp hair (～2.3%). This underestimation in percentage of body fat may be caused by the effect of trapped isothermal air in body hair on body‐volume estimates. Thus, excess facial hair should be kept to a minimum and a swimcap should be worn at all times to ensure accurate estimates of body fat when using the BOD POD.     

Regional body volumes, BMI, waist circumference, and percentage fat in severely obese adults

Objective: This study presents total body volume (TBV) and regional body volume, and their relationships with widely used body composition indices [BMI, waist circumference (WC), and percentage body fat (% fat)] in severely obese adults (BMI ≥35 kg/m²). Research Methods and Procedures: We measured TBV, trunk volume (TV), arm volume (AV), leg volume (LV), and WC and estimated % fat in 32 severely obese persons with BMI 36 to 62 kg/m² (23 women; age, 19 to 65 years; weight, 91 to 182 kg) and in 58 persons with BMI <35 kg/m² (28 women; age, 18 to 83 years; weight, 48 to 102 kg) using a newly validated 3‐day photonic image scanner (3DPS, Model C9036–02, Hamamatsu Co., Japan) and calculated TV/TBV, AV/TBV, and LV/TBV. Results: Men had significantly larger TBV and higher TV/TBV and AV/TBV, but significantly lower LV/TBV than women, independently of BMI. TV/TBV increased while AV/TBV and LV/TBV decreased with increasing BMI, WC, and % fat, and the rate of increase in TV/TBV per % fat was significantly greater in severely obese individuals than in individuals with BMI <35 kg/m². The relationships for TBV with % fat were much lower than with BMI or WC. Conclusion: Body volume gains were mainly in the trunk region in adults, irrespective of sex or BMI. For a given BMI, WC, or % fat, men had a significantly larger TV than women. The implication is that men could have higher health risks due to having higher trunk body weight as a proportion of total body weight compared with severely obese or less severely obese women.     

Calcium and body fat in peripubertal girls: cross-sectional and longitudinal observations

Objective: The objective was to investigate whether calcium intake is independently associated with body fat in peripubertal girls. Research Methods and Procedures: A total of 45 healthy premenarcheal girls (initially 10.5 ± 0.6 years of age) completed a 2‐year prospective observational study. Percent body fat and trunk fat (by DXA), height, weight, maturational stage, and eating attitudes (children's Eating Attitudes Test [EAT]) were measured at baseline and at 1 and 2 years. Physical activity (by questionnaire) and calcium intake (by calcium‐specific food frequency questionnaire and 3‐day food records) were assessed at 6‐month intervals. Results: Girls with 2‐year mean calcium intake below and above the median had similar age, height, lean mass, and maturational stage at baseline, but girls below the median had significantly higher baseline percentage body fat (29.3 ± 10.3% vs. 22.0 ± 6.8%, p < 0.01) and trunk fat (24.2 ± 10.6% vs. 15.8 ± 6.8%, p < 0.01). However, differences were no longer significant when covariates (most notably children's EAT dieting score) were considered. Regression analysis revealed that dieting score was a consistent positive predictor of percentage body and trunk fat at all cross‐sectional time‐points, accounting for >20% of the variance, but did not predict 2‐year change in percentage fat. Calcium intake did not enter longitudinal regression equations for 2‐year change in percentage fat. Discussion: In this group of girls, an inverse cross‐sectional association between calcium intake and body fat appeared to result from avoidance of foods high in calcium by girls who were concerned about their body weight or shape. Calcium intake was not associated with change in fat over time.     

A Prospective Study of Adiposity and All‐Cause Mortality: The Malmö Diet and Cancer Study

Objective: This study aims to examine the association between various measures of adiposity and all‐cause mortality in Swedish middle‐aged and older men and women and, additionally, to describe the influences of age and sex on these associations. Research Methods and Procedures: A prospective analysis was performed in a cohort of 10,902 men and 16,814 women ages 45 to 73 years who participated in the Malmö Diet and Cancer Study in Sweden. Baseline examinations took place between 1991 and 1996, and 982 deaths were documented during an average follow‐up of 5.7 years. All‐cause mortality was related to the following variables measured at baseline: body mass index (BMI), percentage of body fat, lean body mass (LBM), and waist‐to‐hip ratio (WHR), with adjustment for age and selected covariates. Body composition data were derived from bioelectrical impedance analysis. Results: The association between percentage of body fat and mortality was modified by age, particularly in women. For instance, fatness was associated with excess mortality in the younger women but with reduced mortality in the older women. Weaker associations were seen for BMI than for percentage of body fat in both sexes. Placement in the top quintiles of waist‐to‐hip ratio, independent of overall body fat, was a stronger predictor of mortality in women than in men. The observed associations could not be explained by bias from early death or antecedent disease. Discussion: The findings reveal sex and age differences for the effects of adiposity and WHR on mortality and indicate the importance of considering direct measures of adiposity, as opposed to BMI, when describing obesity‐related mortality risks.     

Relationships between Insulin Sensitivity and Measures of Body Fat in Asymptomatic Men and Women

Objective: To assess whether measures of body fat by DXA scanning can improve prediction of insulin sensitivity (S_I) beyond what is possible with traditional measures, such as BMI, waist circumference, and waist‐to‐hip ratio (WHR). Research Methods and Procedures: Frequently sampled intravenous glucose tolerance tests were performed in 256 asymptomatic non‐Hispanic white subjects from Rochester, MN (age 19‐60 years; 123 men and 133 women) to determine the S_I index by Bergman's minimal model technique. Height, weight, and waist and hip circumferences were measured for calculation of BMI and WHR; DXA was used to determine fat in the head, upper body, abdomen, and lower body. Linear regression was used to assess their relationships with S_I after sex stratification and adjustment for age. Results: After controlling for age, increases in traditional and DXA measures of fat were consistently associated with smaller declines in S_I among women than among men. In men, after controlling for age, all of the predictive information of S_I was provided by waist circumference (additional R² = 0.39, p < 0.001); none of the DXA measures improved the ability to predict S_I. In women, after adjustment for age, BMI, and WHR, the only DXA measure that improved the prediction of S_I was percentage head fat (additional R² = 0.03, p < 0.001). Discussion: Equivalent increases in most measures of body fat had lesser impact on S_I in women than in men. In both sexes, the predictive information provided by DXA measures is approximately equal to, but not additive to, that provided by simpler, traditional measures.     

Stability of Adiposity Phenotypes from Childhood and Adolescence into Young Adulthood with Contribution of Parental Measures

Objective: The stability of several indicators of body composition and adipose tissue distribution over 12 years was quantified. Research Methods and Procedures: The participants were 77 boys and 76 girls who were evaluated along with their parents at baseline as children and adolescents (8 to 18 years of age) and remeasured as young adults 12 years later. Indicators of body composition included the body mass index, fat mass, fat free mass, percentage of body fat, sum of six skinfolds (SF6), and the first principal component of six age‐adjusted skinfold residuals. Relative adipose tissue distribution was represented by the second principal component of skinfold residuals and a trunk‐to‐extremity skinfold ratio, adjusted for SF6. Results: Partial interage correlations, controlling for initial age and length of follow‐up, were 0.65 and 0.59 for the body mass index, 0.59 and 0.64 for fat mass, 0.65 and 0.57 for fat free mass, 0.50 and 0.57 for percentage of body fat, 0.66 and 0.44 for SF6, 0.64 and 0.42 for the first principal component of six age‐adjusted skinfold residuals, 0.19 and 0.31 for the second principal component of skinfold residuals, and 0.41 and 0.47 for trunk‐to‐extremity skinfold ratio, adjusted for SF6, in men and women, respectively. Multiple regression analyses indicated that the significant partial R² values of parental measurements on the prediction of their offspring in young adulthood ranged from 2% to 9%. Discussion: The results indicate moderately high stability of indicators of body composition and somewhat lower stability of measures of adipose tissue distribution. Overall, parental measures offer less predictive value than do measures of childhood and adolescent body composition and adipose tissue distribution.     

Prevalence of metabolic syndrome and its relation to body composition in a Chinese rural population

Objective: To investigate the prevalence of metabolic syndrome (MetS) with three different working definitions in a rural Chinese population and to examine its relation to body composition. Research Methods and Procedures: A total of 18,630 adults 25 to 64 years old (mean age, 45.8 years; 51.2% men) from 5686 families were enrolled from Anhui province of China during 2004 to 2005. Anthropometric measurement, body composition, blood pressure, plasma lipids, and fasting glucose and insulin and a questionnaire‐based interview were obtained from each participant. Three different working definitions for MetS, including the U.S. National Cholesterol Education Program's Adult Treatment Panel III, a modified Adult Treatment Panel III that adopts the World Health Organization's criterion for central obesity in Asian populations, and one recently proposed by the International Diabetes Federation, were used in the study. Results: According to the three definitions, the age‐adjusted prevalence of MetS for adults 25 to 64 years old was 3.2%, 4.9%, and 3.9% in men and 7.2%, 11.5%, and 10.9% in women, respectively. MetS prevalence increases significantly with age in women, but not in men. Body fat percentage and BMI and waist circumference were significantly associated with each component of MetS, especially with triglyceride level, insulin resistance index, and number of MetS components (r = 0.28 to 0.49). Discussion: The age‐adjusted prevalence of MetS in our study population is lower than that reported in other urban Chinese populations. Significant gender differences in MetS prevalence were observed. The waist circumference is a good surrogate for abdominal fat percentage.     

Physical activity,energy expenditure and intake in 11 to 12 years old Japanese prepubertal obese boys

The purpose of this study is to find out the differences in physical activity (PA), energy expenditure (EE) and energy intake (EI) under free-living conditions between Japanese prepubertal obese and nonobese boys. The subjects were 15 prepubertal obese boys (Age: 11.7+/-0.4 years old, Body fat: 35.2+/-1.6%) who do not have obese parents and siblings and 15 prepubertal nonobese boys (Age: 11.8+/-0.4 years old, Body fat: 18.5+/-0.8%). We assessed their daily PA by heart rate (HR) monitoring, pedometer step counts (PSC) and time for sedentary activities (SA). We also examined calculated EE from HR-VO(2) regression, EI and percentage of macronutrient EI. Results are as follows: Percentage of body fat had significant correlation with weight, BMI, time for SA, percentage EI of protein (positive, p<0.001), VO(2max), VO(2max) per body weight, VO(2max) per LBM, PSC, TEE per body weight, TEI per body weight (negative, p<0.001), percentage of EI of carbohydrate (negative, p<0.01). The values of the obese were significantly lower in total EE per body weight and in total EI per body weight. EI from dinner was significantly higher in the obese group. The values of the obese were significantly higher in percentage EI from protein and that from carbohydrate. The results of this study showed prepubertal obese boys who do not have obese parents and siblings have low PA and spend much time for sedentary activities. Obese boys consume higher percentage energy of protein and lower percentage of carbohydrate though differences in EE and EI were found only in total EE per body weight and total EI per body weight between obese boys and nonobese boys.     

Body composition of obese subjects by air displacement plethysmography: The influence of hydration

Objective: We investigated whether air displacement plethysmography (ADP) could detect small changes in body composition of obese subjects with alterations in hydration. Research Methods and Procedures: Ten obese subjects (mean BMI, 39.3 ± 2.8 kg/m²) entered the ADP chamber without and with oil (1, 2, or 4 liters), water (1, 2, or 4 liters), or mixed (1 liter oil + 1 liter water or 2 liters oil + 2 liters water) loads. Real and measured changes in body composition were compared by regression analysis and Bland‐Altman procedures. Results: The ADP‐measured changes in volume did not differ from the real values and were strongly correlated with them (r = 0.98). In all cases, loads of differing composition and similar volume led to different values of fat, fat‐free mass, and percentage fat. Water was detected as increased fat‐free mass only with loads of ≥2 liters, most of the water being falsely detected as increased fat mass. The observed changes were correlated with the real ones for fat mass (r = 0.68; p < 0.0001), fat‐free mass (r = 0.66; p < 0.0001), and percentage fat (r = 0.61; p < 0.0001), but fat mass changes were overestimated by ～1 kg, and fat‐free mass changes were underestimated by ～1 kg. This underestimation increased with the highest water loads, as shown by the Bland‐Altman plot (r = ?0.27; p < 0.05). Percentage fat changes were overestimated by 0.8% (p < 0.001); the magnitude of the error was correlated with the weight of the water load (r = 0.62; p < 0.0001). Discussion: ADP accurately measures changes in body volume, discriminating small changes in body composition. It overestimates changes in adiposity, as most of the increased hydration is detected as an enlarged fat mass.     

Efficiency of Walking and Stepping: Relationship to Body Fatness

Objective: To determine energetic efficiency of walking and stepping in a heterogeneous normal adult population and its association with body fatness and to assess within‐ and between‐individual variations. Research Methods and Procedures: Using a combination of a whole‐room indirect calorimeter and a large precision force platform, we simultaneously measured minute‐by‐minute energy expenditure (EE) and mechanical work during walking and stepping in healthy adult men (n = 60) and women (n = 85). Efficiency was calculated as a ratio (percentage) of mechanical work and EE of activity. Efficiency of walking and stepping performed at various intensities was compared for reproducibility within the same day (morning and afternoon) and correlated with a subject's characteristics. Results: The efficiency of walking was negatively correlated with body fatness in both men and women at 0.9 to 1.2 m/s but positively correlated with body fatness in men and not correlated in women at the slowest speed tested (0.6 m/s). Efficiency of walking and stepping of various intensities was reproducible during the same day. Compared at similar EE levels, walking was more efficient than stepping (26% to 27% vs. 18% to 22%, p < 0.01). Women were significantly (p < 0.01) more efficient than men during stepping. Age, sex, body mass, fat‐free mass, fitness (maximal oxygen uptake), height, and speed variations contributed to the between‐subject differences in efficiency. Discussion: Obese individuals were less efficient than lean individuals during normal‐speed walking. Significant interindividual variations in efficiency of walking and stepping may be attributed to habituation and physical characteristics such as age, sex, and fitness level.     

Rate of Fat Gain Is Faster in Girls Undergoing Early Adiposity Rebound

Objective: To determine the changes in body composition (fat and lean mass) occurring in children during adiposity rebound (AR). Research Methods and Procedures: Thirty‐nine girls, 3 to 6 years of age at baseline, underwent yearly DXA scans for 2 years. An additional DXA scan was obtained 4 to 5 years after baseline. Age at AR was determined by modeling, and the velocity of change in height, weight, fat mass, and lean mass was estimated for each child using random coefficient models. Girls with an AR <5 years of age were classified as having an early AR, and those having an AR ≥5 years were classified as late AR. Results: Although body composition was similar at age 5, by age 9, girls with an early AR were significantly taller (3.5% more) and heavier (14.4%), with greater fat mass (50%) and percentage body fat (27%) than girls with a later AR. In addition, more girls were overweight according to BMI (18% vs. 6%) or percentage body fat (29% vs. 11%) at this time, despite no differences at baseline. Annual velocity of fat mass gain was over 2‐fold higher in early compared with late rebounders (17.1% vs. 6.5%, p < 0.0001), with no difference in lean mass velocity (13.1% vs. 12.5%, p = 0.116). Discussion: Differences in BMI during AR were caused specifically by alterations in body fat and not by alterations in lean mass or height. Children undergoing early AR gained fat at a faster rate than children who rebounded at a later age.     

Percentage Fat in Overweight and Obese Children: Comparison of DXA and Air Displacement Plethysmography**

Objective: To compare percentage body fat (percentage fat) estimates from DXA and air displacement plethysmography (ADP) in overweight and obese children. Research Methods and Procedures: Sixty‐nine children (49 boys and 20 girls) 14.0 ± 1.65 years of age, with a BMI of 31.3 ± 5.6 kg/m² and a percentage fat (DXA) of 42.5 ± 8.4%, participated in the study. ADP body fat content was estimated from body density (D_b) using equations devised by Siri (ADP_Siri) and Lohman (ADP_Loh). Results: ADP estimates of percentage fat were highly correlated with those of DXA in both male and female subjects (r = 0.90 to 0.93, all p < 0.001; standard error of estimate = 2.50% to 3.39%). Compared with DXA estimates, ADP_Siri and ADP_Loh produced significantly (p < 0.01) lower estimates of mean body fat content in boys (?2.85% and ?4.64%, respectively) and girls (?2.95% and ?5.15%, respectively). Agreement between ADP and DXA methods was further examined using the total error and methods of Bland and Altman. Total error ranged from 4.46% to 6.38% in both male and female subjects. The 95% limits of agreement were relatively similar for all percentage fat estimates, ranging from ±6.73% to ±7.94%. Discussion: In this study, conversion of D_b using the Siri equation led to mean percentage fat estimates that agreed better with those determined by DXA compared with the Lohman equations. However, relatively high limits of agreement using either equation resulted in percentage fat estimates that were not interchangeable with percentage fat determined by DXA.     

Fat Mass Measured by DXA Varies with Scan Velocity

Objective: To study the influence of scan velocities of DXA on the measured size of fat mass, lean body mass, bone mineral content and density, and total body weight. Research Methods and Procedures: The subjects were 71 healthy white adults, 38 women and 33 men. The mean age was 41.7 ± 13.5 years and body mass index was 28.6 ± 5.6 kg/m². The subjects were scanned consecutively in slow, medium, and fast scan mode by a Lunar DPX-IQ DXA scanner. Results: Throughout the body mass index and sagittal height ranges, scanned lean body mass significantly decreased with higher scan velocity and lean body mass was 2.7% lower in fast than in medium mode (p < 0.0001). In contrast, fat mass, percentage of body fat, and bone mineral contents were higher with increasing scan velocity. Areas not analyzed by the scanner, so called blue spots, increased with scan velocity and sagittal height, and their presence significantly enhanced the error. Body weight estimated by DXA in slow mode was −0.8% lower than scale weight in the women (p < 0.001) and −0.2% in men (not significant), and the difference was greater with increasing scan velocity. Discussion: Scan velocity significantly influences the measured fat mass size, lean body mass, bone mineral content, and body weight. To obtain the most accurate results, slow mode is preferable and fast scans should be avoided. Future studies should report and take scan velocity into consideration.     

Prevalence and Covariates of Obesity in Lebanon: Findings from the First Epidemiological Study

Objective: To estimate the prevalence of overweight and obesity and examine associated covariates in the Lebanese population. Research Methods and Procedures: A cross‐sectional survey of a representative sample of 2104 individuals, 3 years of age and older. Anthropometric measurements and dietary assessments were conducted following standard methods and techniques. Overweight and obesity (classes I to III) were defined according to internationally standardized criteria for classification of BMI. Results: For children 3 to 19 years of age, prevalence rates of overweight and obesity were higher overall for boys than girls (22.5% vs. 16.1% and 7.5% vs. 3.2%, respectively). For adult men and women (age ≥ 20 years), the prevalence of overweight was 57.7% and 49.4%, respectively. In contrast, obesity (BMI ≥ 30 kg/m²) was higher overall among women (18.8%) than men (14.3%), a trend that became more evident with increasing obesity class. BMI, percentage of body fat, and waist circumference increased to middle age and declined thereafter. Whereas lack of exercise associated significantly with obesity among children, obesity in older adults was more prevalent among the least educated, nonsmokers, and those reporting a family history of obesity. Discussion: The results from this national population‐based study in Lebanon show high prevalence rates of overweight and obesity comparable with those observed in developed countries such as the United States. While further studies are needed to examine the underlying social and cultural factors associated with lifestyle and nutritional habits, now is the time to institute multicomponent interventions promoting physical activity and weight control nationwide.     

Differences in basal energy expenditure and obesity

Objective: To assess the impact of differences in basal energy expenditure on adiposity. Research Methods and Procedures: Statistical analysis was performed on a published database giving anthropometric and energy expenditure measurements for 433 women and 335 men. Published equations derived by multiple regression analysis were used to predict basal metabolic rates in women and in men as a function of age, weight, and height. The differences between the observed and predicted rates (i.e., the residuals) were computed and expressed in terms of percentage deviation from the predicted rates of basal energy expenditure (BEE). In addition, individual body fat contents were computed using equations based on National Health and Nutrition Examination Study 3 data relating to body fat content determined by bioimpedance to BMI. Results: There is no correlation between percentage body fat content and deviations from predicted (which one would refer to as normal) BEE. Discussion: It can be concluded that relatively high or relatively low rates of BEE do not influence body weights and adiposity in a statistically identifiable manner. This contradicts and challenges the widely held view that low resting metabolic rates promote the development of obesity.     

Physical Activity as a Predictor of Body Composition in American Indian Children

Objective: To examine physical activity in second grade American Indian children as a predictor of percentage body fat 3 years later. Research Methods and Procedures: Physical activity was assessed as average vector magnitude (AVM) counts from an accelerometer in 454 second grade children as part of the Pathways study. BMI was assessed, and skinfolds and bioelectrical impedance were used to estimate fat mass, fat‐free body mass, and percentage body fat in validated prediction equations. Associations were examined using mixed models regression controlling for baseline body composition. Results: In normal‐weight children, higher AVM counts were significantly associated with decreases in percentage body fat. Among overweight children, higher AVM counts were significantly associated with increases in BMI, fat mass, and fat‐free mass but not percentage body fat. Discussion: Higher physical activity levels in second grade were associated with lower levels of percentage body fat in fifth grade in normal‐weight but not in overweight children. BMI showed no association with physical activity among normal‐weight children, and increases in BMI were associated with increasing amounts of physical activity among overweight children. These findings emphasize the importance of valid body composition measures and may indicate important differences in associations between physical activity and adiposity in normal‐weight as compared with overweight children.